Bolex & Night Photography

23rd September 2003

I'm planning on doing some time lapse shoots with a Bolex. I'm using a light meter that I've never used before, a Minolta IVF.

My question : Since the Bolex should be metered at 1/80th when running at 24 fps, how can I take a 1/80th reading with this meter? It only gives shutter speeds of 45, 60 and 90. How off would I be if I used 1/90th? Luckily the meter can read 1/30th, for the single frames.

My "other" question is more aesthetic...I'm planning on doing some shooting of the moon, and if I can, the stars as well. How long should I expose for, using 250 daylight film (all I have) at an aperture of 2.8 or so? I know there is no simple answer for this, but I don't know how to "meter" the stars. I assume its more of an experience thing, which is why I'm asking here.

Thanks for any answers that can be provided...I'm in northern Quebec doing some editing, and requested a Bolex and an intervalometer to take some shots.

Cheers
Brett Gaylor

>My question : Since the Bolex should be metered at 1/80th when >running at 24 fps, how can I take a 1/80th reading with this meter?

In normal running mode the Bolex shutter speed is really 1/65 second.

The "1/80th" is an interpolation to account for the light loss in the reflex prism. What I have usually done with Bolex is use the 24fps (or whatever) frame rate setting on my meter, and account for the narrower-than-usual shutter speed and prism light loss by rating the film 2/3 stop lower. i.e. EI 200 film rated at 125. etc. This is especially useful if using the Bolex as B camera along with a 172/180 degree shutter mirror reflex camera.

However, experience shows that using these cameras in single frame mode is about the same thing as shooting at 12 fps, i.e. you'll have ~ 1/32 second exposure.

If you're shooting time exposures then the absolute time the shutter is open determines exposure. So only the ~1/3 stop light loss from the prism needs to be calculated.

I've done time exposure of the moon through clouds etc - really depends on focal length, what you want to see around it (clouds etc - in which case you need more doff so smaller aperture = longer exposure = more chance moon detail will be blurred etc).

I fly be the seat of my pants so often in this area I think I'm the wrong person to answer these questions. Well I'm hoping to shoo the full moon reflected in a pool Tuesday night, wacked NJ weather permitting. I guess I could let you know what worked.

Sam Wells

Sam Wells writes :

>In normal running mode the Bolex shutter speed is really 1/65 second

I thought that was true only for reflex Bolexes (Bolices?) in which the prism necessitates some metering compensation in terms of "shutter speed." The older, non-reflex ones should probably clock in at 1/48 or thereabouts, yes?

Dan Drasin
Producer/DP
Marin County, CA

Thanks for writing back, Sam...

>What I have usually done with Bolex is use the 24fps (or whatever) >frame rate setting on my meter, and account for the narrower-than-usual >shutter speed and prism light loss by rating the film 2/3 stop lower.

Right...ie I would rate my 250 at 160? Makes sense...

>I fly be the seat of my pants so often in this area I think I'm the wrong >person to answer these questions.

Me too, just don’t want to be caught out! I'll will also be shooting the moon on Tuesday…so maybe we can compare...trying out this funky "Time Flow" intervalometer from NCS cinema products...

Do you think 1 sec exposure is too much for the moon? Want to try and catch some detail.

Thanks Again

Brett Gaylor

>Right...ie I would rate my 250 at 160? Makes sense...Do you think 1 sec >exposure is too much for the moon? Want to try and catch some detail.

I'm stepping into this one late - so I don't know if I missed some info being bounced around here.

Don't underestimate the brightness of the moon. It is after all reflecting the light of the sun. At a rating of 160 even at a 1/48th shutter speed the moons surface will read around an f11. 1 second is probably a bit "much" methinks unless you're going to ND or stop down.

Roderick
Az. D.P.
www.restevens.com

>Don't underestimate the brightness of the moon. It is after all reflecting >the light of the sun.

Thanks Roderick...I thought I might be overdoing it. I think I'll try somewhere in between to pick up the landscape. Just the kind of advice I was looking for.

Cheers

Brett Gaylor

If you are fortunate enough to live near a planetarium or university with an Astronomy club you should find someone with experience for your exposures, also be careful with the lense you are using, you might experience some fogging of the elements while doing long duration time lapse and also if you exposure time is long you might get some comma aberrations in the stars (if you can shoot any).

If you have access to a planetarium they might be able to lend out to you a manual equatorial mount so you can compensate for the Earth’s rotation, they are also easy to build with hardware store material, but you might not have the time.

They might also be able to provide you with a "lense heater" to help with humidity/fogging of the front element. Best of luck and keep us informed!

Eric Neil Bolté
Montréal based
Cinematographer/Animator

>If you are fortunate enough to live near a planetarium or university with >an astronomy club you should find someone with experience for your >exposures

Thanks Eric....I'm actually in Northern Quebec (Inukjuak) so I'm not near anything...just doing some editing for the NFB, and asked someone to send me up a Bolex...I'm not a professional cinematographer, something more like a hobby time lapser...I'll post my results!

If I'm lucky I'll catch the northern lights, but they're more of a winter thing.

Thanks for the advice!

Brett Gaylor

I don't know about the shutters on non reflex cameras. I think all that info is on Tobin's web site.

1/65 is the actual shutter speed @ 24 on most/all the Rex cameras. 1sec is kind of long but I've done that w/ slower stocks in order to get cloud detail, but a long lens especially, the moon blurs. The earth rotates pretty fast as it turns out.

I know there must be CML threads on this in the archives somewhere.

Motorised equatorial mount would work...

Sam Wells

>If you have access to a planetarium they might be able to lend out to >you a manual equatorial mount so you can compensate for the Earth’s >rotation

A what? I'm having a hard time picturing a "manual" device that works with the earth's rotation. Tell me more.

>they are also easy to build with hardware store material, but you might not >have the time.

How! How! How! Sounds like fun!

Roderick
Az. D.P. (clear skies & all!)

Someone could take a spot reading of the moon on that night, according to your needs(ASA, shutter speed, lens, location etc) and e-mail it to you (since you only have an incident meter) Not the best solution, but an approximation. I recently took readings outdoors for a friend who was shooting miles away and had meter problems, and sent results over the phone. (lol)...

According to some notes I found, time-lapse of the full moon: With Fuji 125T, 1/4 sec exposure (Aaton) I had between T 16 and 22 ( I also used an 85 filter then removed it for other takes) Also, I started after sundown and only after the moon rose quite a bit did the skies go completely black. Try the 75mm Switar(I don't know what options you have) A long telephoto is the best choice but on a Bolex you're somewhat limited in most cases.

So keep it in mind that the full moon is one thing, stars another. If you are shooting the stars alone, you should try really long exposures and bracket up and down I compensated for the earths rotation by framing the moon bottom left of screen, an it ends up at the top right when it exits frame. (Actually, I positioned the moon just out of frame so it "walks in" to frame). Clouds covering the moon and flying by also looked really nice, it gave it that werewolf vibe lol

Humm, I'm now curious as to time lapse of the full moon setting, instead of rising...

Have fun and let us know your results!

Best regards,

John Babl
Miami

Yeah, I spotted the moon last night (because of this conversation) and got an f8. I don't know exactly how accurate that is since the centre spot on the meter is larger than the moon's surface. I still suspect it is more like an 11. I brought out the XL1, set it at 1/30th shutter and even stopped down to 16. There was still no detail on the moon so I had to turn on the ND (9?) and stop down to 5.6-1/3rd

Roderick
Az. D.P.

>Yeah, I spotted the moon last night (because of this conversation) and >got an f8. I don't know exactly how accurate that is since the centre spot >on the meter is larger than the moon's surface…

Roderick, my spot meter goes between 1 an 4 degrees, so I usually mess around with it and compare. Say, I'll do some readings tonight. As I recall, Fuji 125 was a good choice and so would Kodak's 74 (200T).

Of course '18 is a great stock, but for time lapse you'd need ND's at night! lol

John Babl

Hey you guys rock! Thanks Roderick! I’m using Kodak 250D (happens to be what I have up here), 1/30th shutter speed (Bolex single frame), FYI...By XL1 you meant your SLR camera, right, not video? Just wondering, because I did manage to take some shots of the moon using the XL1 DV camera I have up here...is it all right to post pictures to this forum? I could show you the spot I mean to film...

Were you using the ND to increase the contrast/detail on the moon, or just to get the correct F-stop?

Thanks for all of your help...guess I better do a good job with so many DP's behind me now :)

Brett Gaylor

>If you have access to a planetarium they might be able to lend out to >you a manual equatorial mount so you can compensate for the Earth’s >rotation,

If I don't compensate, though, the stars will rotate right? I like the idea of this better!

Brett Gaylor

Brett Gaylor wrote :

>If I don't compensate, though, the stars will rotate right? I like the idea of >this better!

I'm coming in a bit late on this one.

The moon tracks at a different speed in relation to the stars. You would need a equatorial mount with a clock drive set to lunar rate to keep the moon cantered on the crosshairs. Since the moons path varies in the sky the stars will rotate around the moon. If you properly expose for the moon you are not going to see stars. In time-lapse films that have the moon tracking through moving star fields the moon is always a blown out orb. So its the moon or stars not both.

Celestron made an adapter that would allow prime focus photography with a Bolex. It was a T-mount to C-mount adapter. I never tried it. Clear skies in Louisiana are as rare as hens teeth...

Tom McDonnell
DP
New Orleans, La

>By XL1 you meant your SLR camera, right, not video?

No, I mean the XL1 MiniDV camera. I had to put the ND filter on because without it, even stopped down to a 16 it was too bright and there was little to no detail. This was at a slower than normal shutter speed (1/30th) which adds a stop of light too. So I put the ND filter on and then had to open up to a 5.6-1/3rd which gave me just a tad of zebras on the moon's surface.

Roderick
Az. D.P. (gonna try the stars at 1/4th shutter tonight)

Tom McDonnell wrote:

>In time-lapse films that have the moon tracking through moving star >fields the moon is always a blown out orb. So its the moon or stars not >both.

Simple Baby, very easy. Depending on the size of the moon in frame, just put a Center spot ND filter on it. Might need a large filter and matte box to position it correctly, but it really doesn't sound all that hard.

Steven Gladstone
Cinematographer - Gladstone Films
Cinematography Mailing List - East Coast List Administrator
Better off Broadcast (B.O.B.)
New York, U.S.A.

Tom McDonnell said :

>In time-lapse films that have the moon tracking through moving star >fields the moon is always a blown out orb. So its the moon or stars not >both.

Steven said :

>Simple Baby, very easy. Depending on the size of the moon in frame, >just put a Center spot ND filter on it.

Yes, but sadly that's only if you are going to track with the moon. Sounds like fun though. I still want to know how to build me one of those manual earth orbit spinny thingies and then that's exactly what I would do (the ND spot for los Luna).

Roderick
Az. D.P.
12 On / 12 Off!

Hey Guys,

Sorry it took me a while, as some of you know I am in the process of packing up my things since I am leaving for Frankfurt am Main this Wednesday and I am also finishing up post-prod on a shoot.....couldn’t readily find & scan my original drawings but here is a link with a very similar device + great explanations, does not take too much of a stretch to adapt it to time lapse photography with lightweight cine or video gear (mine works fine on a Bolex and Mitchell !)

Here’s the link http://www.astronomyboy.com/barndoor/index.html

Eric Neil Bolte

>The moon tracks at a different speed in relation to the stars. You would >need a equatorial mount with a clock drive set to lunar rate to keep the >moon cantered on the crosshairs.

Let me get this straight...there is a lens mount that rotates with the moon to keep it static in the frame?

I want one.

Brett Gaylor

Steven Gladstone wrote :

>Depending on the size of the moon in frame, just put a Center spot ND >filter on it.

Or the easy solution, fix it in post !

Tom McDonnell
DP
New Orleans, La

No, I mean the XL1 MiniDV camera.

Huh....out of curiosity, what film stock does the XL1 compare to? I have some shots of the moon that I just took, check them out on my website......

http://www.etherworks.ca/journal.shtml

scroll down the page a bit....

One of those moon shots is 1/60th wide open, the other, I believe, is at 1/30th wide open. I might be mistaken, but I seem to remember dialling it open as far is it would go...These are exported from FCP, not the snazziest resolution.

Brett Gaylor

Brett Gaylor wrote :

>there’s a lens mount that rotates with the moon to keep it static in the >frame?

Not quite. You would mount the entire Bolex camera assembly onto the mounting. To make all this work properly you have to line up on the north pole star Polaris. The Little Dippers handle ends on Polaris. The right ascension axis is sighted to the pole star with some sort of sighting instrument say a 8x50 finder scope. They make very simple platforms that are designed for 35mm still cameras. Your Bolex would be light enough to work.

You could search Google under camera platform and Astrophotography.

Since the star field is stationary in relation to the camera you could do very long exposures of the stars with no star trailing. The clock drive drives the mount at the exact speed the Earth rotates only in the opposite direction hence rendering the sky static from the cameras perspective.

It's been a long time since I've looked thru a telescope. Have fun with it.

Tom McDonnell
DP
New Orleans, La

The way I would recommend is do some tests with a still camera. Take several pictures at different stops, record what you do for each shot. If you can find someone with a densitometer to get better results as most prints are corrected by the lab automatically, and from this you should be able to figure out nearly exact exposure needed.

Something I am wondering about is the effect of a polo filter on the moon and stars. Has anyone tried that? If not I think I might, the next time I see the moon.

Richie Schut
AC and Multimedia Addict
Washington State

Brett asked :

>Huh....out of curiosity, what film stock does the XL1 compare to? I have >some shots of the moon that I just took

>One of those moon shots is 1/60th wide open, the other, I believe, is at >1/30th wide open.

Firstly. The XL1's "ASA-like" rating generally falls between 250 and 400 depending on chosen stop, color balance, etc.

Note that the first of your two shots the moon has quite the orange color indicating its low position on the horizon with a fair amount of "atmosphere" helping to diffuse it or dim it down. In other words it probably wouldn't have spotted at an 11 at that moment. I would guess more like an f5.6. What is "wfo" on your lens? I know on my Canon EOS with Tamron 28-200mm it is effectively a 5.6. If your's is similar then it all adds up pretty well.

Also note that in the second picture the color is toned down quite a bit indicating less atmosphere to scrim it down and you can see little to no detail on the moon. It was probably reading more like an 8 or 11 there and if you would have stopped down you may have seen better detail on it.

Having conversed about stopping down for the moon, I am presently kicking myself for shooting some 35mm time lapse of lighting two nights ago WFO (t1.4) well - let's hope for latitude.

Roderick
Az. D.P.
12 On / 12 Off!

There are some nice night time lapse shots with the moon and stars in "Baraka". I think it was shot in 65mm?.

Good luck on your experience!

Sincerely,

Agustin Barrutia,
Electrician/Cinematography student.
Buenos Aires, Argentina.

>Note that the first of your two shots the moon has quite the orange color >indicating its low position on the horizon with a fair amount of >"atmosphere" helping to diffuse it or dim it down.

I shot the moon w/ the XL-1 last night at midnight, when the sky was clear...I definitely had to stop down quite a bit...thanks for helping me think out loud on this one!

Brett Gaylor

The moon is in direct sunlight, so the f/16 rule applies nicely.

If your subject is in direct sunlight, and your lens is set to f/16, the reciprocal of the film speed is in the correct shutter speed.

This (like incident measurements) assumes the overall scene reflectivity is the same as an 18% grey card. The moon is a little bit lighter overall, but you're shooting color negative so you can take advantage of the highlight compensation that negative stock buys you.

Scott

Brett Gaylor writes:

>Let me get this straight...there is a lens mount that rotates with the moon >to keep it static in the frame?

What's being suggested is to put your camera on an "equatorial mount." This is the most common type of mounting system for astronomical telescopes. It has a rotation axis and a tilt axis. The rotation axis is aligned with the earth's axis (by aiming it at the North Star), and a clock-motor drive is employed to rotate the telescope "backwards" vis-a-vis the earth's rotation, so the 'scope (or camera) remains aligned with the fixed stars rather than the earth.

The other type of telescope mount is called "altazimuth." An ordinary tripod head is an example of this type: One axis determines "altitude" (vertical tilt) and the other "azimuth" (compass direction). Altazimuth mounts are simpler and stronger, but In order to track the fixed stars they must be -- for fairly obvious reasons -- computer-driven.

To track the moon, even an equatorial mount must be computer-driven -- to match the moon's complex motion.

Hope this clears up the mystery!

As has been said, though, the moon is quite bright enough not to require sophisticated tracking for purposes of still photography. In fact, I believe that the lunar surface is considered to be the most retro reflective natural substance known -- probably somewhat like the tiny glass beads on a beaded projection
screen.

Dan Drasin
Producer/DP
Marin County, CA

>the lunar surface is considered to be the most retro reflective natural >substance known

That scares me...visions of Pepsi ads on the moon before I'm 80...

Brett Gaylor

>The moon is a little bit lighter overall

>I believe that the lunar surface is considered to be the most retro >reflective natural substance known

The Moon's average surface reflectance is 7%. It can hardly be considered "bright". The Moon's apparent brightness is due to the fact we normally see it wholly, as a spot against the dark sky and the fact it has no atmosphere to absorb the Sun's light. Once you get close to its surface, as seen through a powerful telescope, the smaller the fraction of its circle, the darker it gets to the eye and the longer the exposure needed for its photography.

If you want a good reflectance in a planetary body, go for Jupiter, Saturn or, specially, Venus (clouds, as well as ice are the best surfaces for reflection; dark grey dust is not).

Arturo Briones-Carcaré
Filmmaker
Madrid (Imperial Spain)